Correcting touch interference for active pen

ABSTRACT

A method of capacitive sensing includes obtaining a capacitive touch profile from multiple receiver electrodes disposed in a sensing region of an input device and obtaining an active pen profile, different from the capacitive touch profile, from the multiple receiver electrodes. The method also includes adjusting, using the capacitive touch profile, the active pen profile to obtain a corrected active pen profile and determining a position of an active pen in the sensing region, using the corrected active pen profile.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application of, and therefore,claims benefit under 35 U.S.C. 119(e), to U.S. Patent Application Ser.No. 63/224,368, filed on Jul. 21, 2021. U.S. Patent Application Ser. No.63/224,368 is incorporated by reference in its entirety.

TECHNICAL FIELD

The described embodiments relate generally to electronic devices, andmore specifically, to improving the performance of capacitive imagingsensors when used in conjunction with active pens in presence of touch.

BACKGROUND

Input devices including proximity sensor devices (e.g., touchpads ortouch sensor devices) are widely used in a variety of electronicsystems. A proximity sensor device typically includes a sensing region,often demarked by a surface, in which the proximity sensor devicedetermines the presence, location and/or motion of one or more inputobjects. Proximity sensor devices may be used to provide interfaces forthe electronic system. For example, proximity sensor devices are oftenused as input devices for larger computing systems (such as opaquetouchpads integrated in, or peripheral to, notebook or desktopcomputers). Proximity sensor devices are also often used in smallercomputing systems (such as touch screens integrated in cellular phones).

Proximity sensor devices utilize one or more electrical techniques, suchas a capacitive sensing technique, to determine the presence, locationand/or motion of an input object. The proximity sensor devices often usean array of sensor electrodes arranged in a sensor pattern to detect thepresence, location and/or motion of an input object.

An input object may be a finger, an active pen, etc. Multiple inputobjects may be simultaneously used in conjunction with a proximitysensor device. For example, a finger or a palm may rest on the surfaceof the proximity sensor device, while input may be provided with anactive pen. The presence of the finger or palm may cause touchinterference, resulting in a degradation of the input provided by theactive pen.

Therefore, it is desirable to provide methods and systems to address thetouch interference.

SUMMARY

In general, in one aspect, one or more embodiments relate to a method ofcapacitive sensing. The method includes obtaining a capacitive touchprofile from multiple receiver electrodes disposed in a sensing regionof an input device and obtaining an active pen profile, different fromthe capacitive touch profile, from the multiple receiver electrodes. Themethod also includes adjusting, using the capacitive touch profile, theactive pen profile to obtain a corrected active pen profile anddetermining a position of an active pen in the sensing region, using thecorrected active pen profile.

In another aspect, one or more embodiments relate to an input devicethat includes multiple receiver electrodes disposed in a sensing regionand a processing system. The processing system is configured to obtain acapacitive touch profile from the multiple receiver electrodes andobtain an active pen profile, different from the capacitive touchprofile, from the multiple receiver electrodes. The processing system isfurther configured to adjust, using the capacitive touch profile, theactive pen profile to obtain a corrected active pen profile and todetermine a position of an active pen in the sensing region, using thecorrected active pen profile.

In another aspect, one or more embodiments relate to a processingsystem, configured to obtain a capacitive touch profile from multiplereceiver electrodes disposed in a sensing region of an input device andto obtain an active pen profile, different from the capacitive touchprofile, from the multiple receiver electrodes. The processing system isfurther configure to adjust, using the capacitive touch profile, theactive pen profile to obtain a corrected active pen profile and todetermine a position of an active pen in the sensing region, using thecorrected active pen profile.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a block diagram of an input device, in accordance with oneor more embodiments.

FIG. 2A and FIG. 2B show capacitive sensing scenarios in accordance withone or more embodiments.

FIG. 3A and FIG. 3B show touch coupling models, in accordance with oneor more embodiments.

FIG. 4A and FIG. 4B show example quadrature demodulations, in accordancewith one or more embodiments.

FIG. 5 shows a correction of an active pen profile, in accordance withone or more embodiments.

FIG. 6A and FIG. 6B show examples of corrections of active pen profiles,in accordance with one or more embodiments.

FIG. 6C, FIG. 6D, and FIG. 6E show examples of adjacent values in activepen profiles, in accordance with one or more embodiments.

FIG. 7 shows a flowchart, in accordance with one or more embodiments.

FIG. 8 shows a flowchart, in accordance with one or more embodiments.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature, and isnot intended to limit the disclosed technology or the application anduses of the disclosed technology. Furthermore, there is no intention tobe bound by any expressed or implied theory presented in the precedingtechnical field, background, or the following detailed description.

In the following detailed description of embodiments, numerous specificdetails are set forth in order to provide a more thorough understandingof the disclosed technology. However, it will be apparent to one ofordinary skill in the art that the disclosed technology may be practicedwithout these specific details. In other instances, well-known featureshave not been described in detail to avoid unnecessarily complicatingthe description.

Throughout the application, ordinal numbers (e.g., first, second, third,etc.) may be used as an adjective for an element (i.e., any noun in theapplication). The use of ordinal numbers is not to imply or create anyparticular ordering of the elements nor to limit any element to beingonly a single element unless expressly disclosed, such as by the use ofthe terms “before”, “after”, “single”, and other such terminology.Rather, the use of ordinal numbers is to distinguish between theelements. By way of an example, a first element is distinct from asecond element, and the first element may encompass more than oneelement and succeed (or precede) the second element in an ordering ofelements.

Various embodiments of the present disclosure provide input devices andmethods for the sensing of touch (e.g., of a finger) and the detectionof an active pen. Touch and active pen may be simultaneously present ina sensing area, and the presence of a finger or palm may cause touchinterference, resulting in a degradation of the input provided by theactive pen as discussed in reference to FIGS. 2 and 3 . One or moreembodiments of the disclosure perform operations to correct for thetouch interference, thereby enabling an accurate detection of an activepen in presence of touch, in the sensing area.

FIG. 1 is a block diagram of an example of an input device (100), inaccordance with one or more embodiments. The input device (100) may beconfigured to provide input to an electronic system (not shown). As usedin this document, the term “electronic system” (or “electronic device”)broadly refers to any system capable of electronically processinginformation. Some non-limiting examples of electronic systems includepersonal computers, such as desktop computers, laptop computers, netbookcomputers, tablets, web browsers, e-book readers, smart phones, personaldigital assistants (PDAs), gaming devices, automotive infotainmentsystems, etc.

In FIG. 1 , the input device (100) is shown as a proximity sensor device(e.g., “touchpad” or a “touch sensor device”) configured to sense inputprovided by one or more input objects (140) in a sensing region (120).Example input objects include styli, an active pen, and a finger (142).Further, which particular input objects are in the sensing region maychange over the course of one or more gestures.

The sensing region (120) encompasses any space above, around, in and/ornear the input device (100) in which the input device (100) is able todetect user input (e.g., user input provided by one or more inputobjects). The sizes, shapes, and locations of particular sensing regionsmay vary widely from embodiment to embodiment.

The input device (100) may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region(120). The input device (100) includes one or more sensing elements fordetecting user input. As a non-limiting example, the input device (100)may use capacitive techniques.

In some capacitive implementations of the input device (100), voltage orcurrent is applied to create an electric field. Nearby input objectscause changes in the electric field, and produce detectable changes incapacitive coupling that may be detected as changes in voltage, current,or the like.

Some capacitive implementations utilize arrays or other regular orirregular patterns of capacitance sensing elements to create electricfields. In some capacitive implementations, separate sensing elementsmay be ohmically shorted together to form larger sensor electrodes. Somecapacitive implementations utilize resistive sheets, which may beuniformly resistive.

Some capacitive implementations utilize “self capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes and an input object. In variousembodiments, an input object near the sensor electrodes alters theelectric field near the sensor electrodes, thus changing the measuredcapacitive coupling. In one implementation, an absolute capacitancesensing method operates by modulating sensor electrodes with respect toa reference voltage (e.g., system ground), and by detecting thecapacitive coupling between the sensor electrodes and input objects. Thereference voltage may by a substantially constant voltage or a varyingvoltage and in various embodiments; the reference voltage may be systemground. Measurements acquired using absolute capacitance sensing methodsmay be referred to as absolute capacitive measurements.

Some capacitive implementations utilize “mutual capacitance” (or “transcapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes. In various embodiments, an inputobject near the sensor electrodes alters the electric field between thesensor electrodes, thus changing the measured capacitive coupling. Inone implementation, a mutual capacitance sensing method operates bydetecting the capacitive coupling between one or more transmitter sensorelectrodes (also “transmitter electrodes” or “transmitter”, Tx) and oneor more receiver sensor electrodes (also “receiver electrodes” or“receiver”, Rx). Transmitter sensor electrodes may be modulated relativeto a reference voltage (e.g., system ground) to transmit transmittersignals. Receiver sensor electrodes may be held substantially constantrelative to the reference voltage to facilitate receipt of resultingsignals. The reference voltage may be a substantially constant voltageand in various embodiments, the reference voltage may be system ground.In some embodiments, transmitter sensor electrodes and receiver sensorelectrodes may both be modulated. The transmitter electrodes aremodulated relative to the receiver electrodes to transmit transmittersignals and to facilitate receipt of resulting signals. A resultingsignal may include effect(s) corresponding to one or more transmittersignals, and/or to one or more sources of environmental interference(e.g., other electromagnetic signals). The effect(s) may be thetransmitter signal, a change in the transmitter signal caused by one ormore input objects and/or environmental interference, or other sucheffects. Sensor electrodes may be dedicated transmitters or receivers,or may be configured to both transmit and receive. Measurements acquiredusing mutual capacitance sensing methods may be referred to as mutualcapacitance measurements.

In FIG. 1 , a processing system (110) is shown as part of the inputdevice (100). The processing system (110) is configured to operate thehardware of the input device (100) to detect input in the sensing region(120). One or more of the steps described in the flowcharts of FIG. 7and FIG. 8 may be performed by the processing system (110). Theprocessing system (110) includes parts of or all of one or moreintegrated circuits (ICs) and/or other circuitry components. Forexample, a processing system for a mutual capacitance sensor device mayinclude transmitter circuitry configured to transmit signals withtransmitter sensor electrodes, and/or receiver circuitry configured toreceive signals with receiver sensor electrodes. Further, a processingsystem for an absolute capacitance sensor device may include drivercircuitry configured to drive absolute capacitance signals onto sensorelectrodes, and/or receiver circuitry configured to receive signals withthose sensor electrodes. In one or more embodiments, a processing systemfor a combined mutual and absolute capacitance sensor device may includeany combination of the above described mutual and absolute capacitancecircuitry. In some embodiments, the processing system (110) alsoincludes electronically-readable instructions, such as firmware code,software code, and/or the like.

The processing system (110) may be implemented as a set of modules thathandle different functions of the processing system (110). For example,the processing system (110) may include determination circuitry (150) todetermine when at least one input object is in a sensing region,determine signal-to-noise ratio (SNR), determine positional informationof an input object, identify a gesture, determine an action to performbased on the gesture, a combination of gestures or other information,and/or perform other operations. The modules may include hardware and/orsoftware which may execute on a processor.

The sensor circuitry (160) may include functionality to drive thesensing elements to transmit transmitter signals and receive theresulting signals. For example, the sensor circuitry (160) may includesensory circuitry that is coupled to the sensing elements. The sensorcircuitry (160) may include, for example, a transmitter module and areceiver module. The transmitter module may include transmittercircuitry that is coupled to a transmitting portion of the sensingelements. The receiver module may include receiver circuitry coupled toa receiving portion of the sensing elements and may includefunctionality to receive the resulting signals.

Although FIG. 1 shows determination circuitry (150) and sensor circuitry(160), alternative or additional modules may exist in accordance withone or more embodiments. Example alternative or additional modulesinclude hardware operation modules for operating hardware such as sensorelectrodes and display screens (155), data processing modules forprocessing data such as sensor signals and positional information,reporting modules for reporting information, and identification modulesconfigured to identify gestures, such as mode changing gestures, andmode changing modules for changing operation modes.

In some embodiments, the processing system (110) responds to user input(or lack of user input) in the sensing region (120) directly by causingone or more actions. Example actions include changing operation modes,as well as graphical user interface (GUI) actions such as cursormovement, selection, menu navigation, and other functions. In someembodiments, the processing system (110) provides information about theinput (or lack of input) to some part of the electronic system (e.g., toa central processing system of the electronic system that is separatefrom the processing system (110), if such a separate central processingsystem exists). In some embodiments, some part of the electronic systemprocesses information received from the processing system (110) to acton user input, such as to facilitate a full range of actions, includingmode changing actions and GUI actions.

In some embodiments, the input device (100) includes a touch screeninterface, and the sensing region (120) overlaps at least part of anactive area of a display screen (155). For example, the input device(100) may include substantially transparent sensor electrodes overlayingthe display screen and provide a touch screen interface for theassociated electronic system. The display screen may be any type ofdynamic display capable of displaying a visual interface to a user, andmay include any type of light emitting diode (LED), organic lightemitting diode (OLED), microLED, liquid crystal display (LCD), or otherdisplay technology. The input device (100) and the display screen mayshare physical elements. For example, some embodiments may utilize someof the same electrical components for displaying and sensing. In variousembodiments, one or more display electrodes of a display device may beconfigured for both display updating and input sensing. As anotherexample, the display screen may be operated in part or in total by theprocessing system (110).

While FIG. 1 shows a configuration of components, other configurationsmay be used without departing from the scope of the invention. Forexample, various components may be combined to create a singlecomponent. As another example, the functionality performed by a singlecomponent may be performed by two or more components.

Turning to FIG. 2A, a capacitive sensing scenario is shown in accordancewith one or more embodiments. The capacitive sensing scenario (200)involves the simultaneous presence of a palm or finger (290) and anactive pen (280) in the sensing region (120). Sensing operations may beperformed using the first electrodes (202), aligned with a first (orvertical) axis, and the second electrodes (204), aligned with a second(or horizontal) axis, to determine the location of the palm or finger(290) and the location of the active pen (280). In the example of FIG.2A, the first and second electrodes (202, 204) are in the shape ofvertical and horizontal bars, respectively. Other electrode shapes andpatterns may be used, without departing from the disclosure.

A capacitive sensing operation (e.g., absolute capacitance sensing,mutual capacitance sensing, etc.) may be performed to determine thelocation of the palm or finger (290).

In one or more embodiments, the first electrodes (202) and/or the secondelectrodes (204) are used for an absolute capacitance sensing method tolocalize an input object such as the palm or finger (290). A presence orabsence of the palm or finger (290) near the first and/or second sensorelectrodes (202, 204) alters the electric field near the sensorelectrodes, thus changing the measured capacitive coupling. The changeof the capacitive coupling may be measured across columns formed by thefirst electrodes (202) and/or across rows formed by the secondelectrodes (204), thereby forming absolute capacitance touch profiles. Acapacitive image that may span the entire sensing region (120) may beformed by the changes of the capacitive couplings measured across therows and columns. Other forms of capacitive sensing may be used, withoutdeparting from the disclosure. For example, a transcapacitance sensingmay be used.

In one or more embodiments, the first and the second electrodes (202,204) may be used as receiving electrodes to receive a pen signal emittedby the active pen (280). The location of the active pen (280) may bedetermined based on the amplitude of the pen signal received by thefirst and second electrodes (202, 204). Active pen profiles may, thus,be generated, analogous to the capacitive touch profiles, and thecombination of the active pen profiles may form an active pen image. Adirect spatial correspondence may exist between active pen profiles andcapacitive touch profiles. In other words, for a value of the capacitivetouch profile at a particular location, a corresponding value of theactive pen profile at the same location may exist. Additional detailsregarding the obtaining of the location of the active pen (280) areprovided below.

Turning to FIG. 2B, a capacitive sensing scenario, in accordance withone or more embodiments, is shown. In the capacitive sensing scenario(250), a user rests a palm or finger (290) in the sensing region (120).While the palm or finger (290) is resting in the sensing region, theuser draws geometric shapes that include lines using the active pen(280). In one or more embodiments, when operating the input device (100)with an activated compensation, the lines (296) are straight, with noartifacts. However, when operating the input device (100) with adeactivated compensation, the lines (292) include jagged line artifacts(294). In the example the jagged line artifacts (294) appear in a regiondelimited by the two horizontal lines, in FIG. 2B. The two horizontallines may represent the vertical extent of the touch of the palm orfinger (290). Accordingly, the touch of the sensing region (120) by thepalm or finger (290) may interfere with the processing of the pensignal.

Causes for the jagged line artifacts (294) are subsequently discussed inreference to FIGS. 3A and 3B. Further, the compensation for theinterference by the touch is described in reference to FIGS. 3A, 3B, 4A,4B, 5, 6A, 6B, 6C, 6D, 6E, and 7 .

Turning to FIG. 3A, a touch coupling model, in accordance with one ormore embodiments, is shown. The touch coupling model (300) includes anactive pen (310) transmitting a pen signal (396) that is received by areceiver electrode (320). The pen signal (e.g., a square wave) may beemitted at a pen tip (314). To compensate for the fluctuation of theelectric potential causing the emission of the pen signal (396) at thepen tip (314), the electric potential of the pen body (312) mayfluctuate inversely to the electric potential at the pen tip (314).Accordingly, the pen body (312) may emit an inverted pen signal (398).

FIG. 3A includes three capacitances to show how the pen signal (396) andthe inverted pen signal (398) may be received by the receiver electrode(320). Assume that the receiver electrode (320) is one of the secondelectrodes (204) in FIG. 2A. More specifically, assume that the receiverelectrode (320) is one of the second electrodes that is in closeproximity to the pen tip (314) and the palm or finger (290, in FIG. 2A).In this case, a capacitance, C_(pen2s), provides a capacitive couplingbetween the pen tip (314) and the receiver electrode (320). Accordingly,the pen signal (396) may couple onto the receiver electrode (320) viaC_(pen2s). Further, a capacitance, C_(pen2hand), provides a capacitivecoupling between the pen body (312) and the user's hand. A capacitance,C_(hand2s), provides a capacitive coupling between the user's hand andthe receiver electrode (320), and a capacitance, C_(hand2sysgnd),provides a capacitive coupling between the user's hand and the systemground (GND). Accordingly, the inverted pen signal (398) may couple ontothe receive electrode via C_(pen2hand) and C_(hand2s). As a result, theinverted pen signal (398) may interfere with the pen signal (396), onthe receiver electrode (320). The degree of interference may depend onvarious factors, as subsequently discussed.

With a good coupling between the hand and the system GND,C_(hand2sysgnd) may dominate over C_(hand2s). In this case, not much ofthe inverted pen signal (398) may couple onto the receiver electrode(320), and the interference caused by the inverted pen signal (398) may,thus, be negligible. However, with a poor coupling between the hand andthe system GND, the coupling of the inverted pen signal (398) onto thereceiver electrode (320) may be non-negligible. To gain further insightinto the coupling of inverted pen signal (398) onto the receiverelectrode (320), the touch coupling model (300), shown in FIG. 3A, maybe represented by an equivalent touch coupling model in FIG. 3B.

Turning to FIG. 3B, a touch coupling model (350), in accordance with oneor more embodiments, is shown. The touch coupling model (350) may beunderstood as equivalent to the model (300) shown in FIG. 3A. C₁ is theequivalent capacitor responsible for the coupling of the inverted pensignal (398) onto the receiver electrode (320). C₂ does not provideadditional coupling of the inverted pen signal (398) onto the receiverelectrode (320). As a result, C₃ also does not contribute to thecoupling of the inverted pen signal (398) onto the receiver electrode(320). With C₁ removed, no coupling of the inverted pen signal (398)onto the receiver electrode (320) would occur. Due to the equivalence ofthe circuit of FIG. 3A and the circuit of FIG. 3B, C₁ may be calculatedas follows:

$C_{1} = {\frac{C_{{pen}2{hand}} \times C_{{hand}2s}}{C_{{pen}2{hand}} + C_{{hand}2s} + C_{{hand}2{sysgnd}}}.}$

C_(hand2s) may be measured, e.g., using an absolute capacitancemeasurement. C_(pen2hand), in a first approximation, may be assumed tobe constant, although some variation may exist, depending on how andwhere the pen is held by the user. C_(hand2sysgnd) may be measured, andmay, thus, also assumed to be known. Accordingly, in the above equation,C₁ may be calculated. C₁ may be expressed as a measurement of C_(hand2s)in the numerator multiplied by a gain formed by the other terms of theabove equation, i.e., C₁=gain*C_(hand2s), where

${gain} = {\frac{C_{{pen}2{hand}}}{C_{{pen}2{hand}} + C_{{hand}2s} + C_{{hand}2{sysgnd}}}.}$

Rewritten in this form, this suggests that a correction of an active penprofile that is affected through interference by touch may be obtainedthrough adjustment of the active pen profile using the capacitive touchprofile, scaled by the gain. As the touch coupling model (300) suggests,the gain depends on C_(hand2sysgnd). For a high C_(hand2sysgnd), thegain approaches zero. In other words, under good ground mass conditions,the gain may be zero, or near-zero, thus providing no or littlecorrection to obtain an accurate corrected active pen profile. However,under low ground mass (LGM) conditions, the gain may be significant,thus providing the correction to adjust the active pen profile for thepresence of touch. Ground mass refers to the electrical coupling to freespace (e.g., air or vacuum). Large objects, such as a human body or avehicle, have good coupling to free space due to a large surface areafor coupling. Unless connected to a power supply or sitting on a largeconductive surface, a phone has much less coupling to free space due tothe small size of the phone. This is often referred to as low groundmass (LGM). Thus, a phone placed on a pillow or cardboard box has verylow ground mass. However, if a person holds a phone in one hand, thephone has a good ground.

Those skilled in the art will appreciate that the touch coupling models(300, 350) are simplified representations of an actual capacitivesensing scenario. Other models may model additional details and may,thus, include additional resistances, capacitances, etc., withoutdeparting from the disclosure.

The following discussion describes correcting an active pen profile thatis affected by the presence of touch, in accordance with one or moreembodiments. Multiple steps may be performed. Broadly speaking, (i) acapacitive touch profile is obtained, (ii) an active pen profile isobtained, and (iii) a corrected active pen profile is obtained byadjusting the active pen profile using the capacitive touch profile. Thecorrected active pen profile may be used to determine the position ofthe active pen, in the sensing region. The highest value in the activepen profile may be indicative of the position of the active pen. Aspatial interpolation may be used to interpolate between adjacentvalues.

The capacitive touch profile may be obtained, e.g., by performingabsolute capacitance sensing as previously described.

Further the active pen profile may be obtained as previously described.In one or more embodiments, the active pen signal may emit a pen signalthat is not synchronized with the demodulation circuits of the inputdevice. Accordingly, a quadrature demodulation may be performed to allowproper measurement of the amplitude of the pen signal received by thereceiver electrodes of the input device.

FIGS. 4A and 4B show quadrature demodulations, in accordance with one ormore embodiments.

Turning to FIG. 4A, the example quadrature demodulation (400) is shownfor an active pen profile over multiple receiver electrodes. At eachreceiver electrode, four values are obtained, using demodulationoperations with different delays (0°, 90°, 180°, 270°) of the quadraturedemodulation. In the example, assume that the active pen is located nearreceiver electrode 5, and further assume that a finger is located nearreceiver electrode 13. In one or more embodiments, the quadraturedemodulation involves computing a single value (amplitude) for each ofthe receiver electrodes. Single values may be obtained by firstidentifying a maximum delta across all receiver electrodes. In theexample, the maximum delta is found for the values obtained at a 90°delay and a 180° delay, at electrode 5. Next, the delta is computed forthe delays at which the maximum delta was identified. Accordingly, inFIG. 4A, the trace for the 90° delay is subtracted from the trace forthe 180° delay.

Turning to FIG. 4B, the example quadrature demodulation (450) is aresult of the described operations for obtaining a single value for eachof the receiver electrodes. The resulting active pen profile includes apeak at the location of the active pen (electrode 5), and preserves adip at the location of the finger, which may represent the inverted pensignal coupled onto the electrode by the finger (electrode 13).

While a specific type of quadrature demodulation has been described,other types of quadrature demodulation may be performed, withoutdeparting from the disclosure.

Turning to FIG. 5 , a correction of an active pen profile (500), inaccordance with one or more embodiments, is shown. The left half of FIG.5 shows a schematic representation of a sensing region withvertically-oriented electrodes on the vertical axis in a configurationfor active pen profile sensing. The right half of FIG. 5 shows aschematic representation of the sensing region with thevertically-oriented electrodes on the vertical axis in a configurationfor capacitive touch profile sensing. In FIG. 5 , an input object 540 inthe sensing region is in contact with receiver electrodes 505, 511, 512,and 513. In an example, the input object 540 may be the palm of a userthat causes a “negative palm disturbance” that extends from at leastreceiver electrode 511 to at least receiver electrode 505 in the penprofile (left half of FIG. 5 ). The input object 540 may also cause a“positive palm disturbance” that extends from at least receiverelectrode 511 to at least receiver electrode 505 in the touch profile.

As previously discussed in reference to FIGS. 3A and 3B, the correctionmay be performed by adjusting a value of the active pen profile byadding the corresponding value of the capacitive touch profile, scaledby a gain:

${{gain} = \frac{c_{{pen}2{hand}}}{c_{{pen}2{hand}} + c_{hand2s} + c_{{hand}2{sysgnd}}}},$

as previously introduced.

The gain may be identified as follows. Assume that the operation isperformed for electrode n. The active pen profile value for electrode nis D_(n). (left half of FIG. 5 ). Thus, the active pen profile value forreceiver electrode 511 is D₀, the active pen profile value for receiverelectrode 512 is D₁, and the active pen profile value for receiverelectrode 513 is D₂. D₀, D₁, and D₂ represent the profile regionassociated with the “pen peak” location near the top of the pen profileregion in the left half of FIG. 5 .

The capacitive touch profile value for electrode n is E_(n) (right halfof FIG. 5 ). Thus, the capacitive touch profile value for receiverelectrode 511 is E₀, the capacitive touch profile value for receiverelectrode 512 is E₁, and the capacitive touch profile value for receiverelectrode 513 is E₂.

A corrected active pen profile value for electrode n, D_(n)′ may beobtained by the operation D_(n)′=D_(n)+E_(n)*Gain. The gain may bedetermined based on profile values outside the shaded profile region D(represented by D₀, D₁, and D₂) in the left half of FIG. 5 . By way ofexample, the receiver electrode 505 is outside the profile region D andhas an active pen profile value of A_(tmax) (see left half of FIG. 5).The receiver electrode 505 also has a capacitive touch profile value ofB_(tmax) (see right half of FIG. 5 ). Under this condition,Gain=−A_(tmax)/B_(tmax).

The gain may be dynamically calculated. If the required input object(e.g., palm or finger) region is not available for updating the gain,the last known gain may be used. This may occur, for example, when thelocation of the pen in the active pen profile/capacitive touch profilecoincides with the location of the palm or finger. Referring to FIG. 5 ,this would occur with the pen at the location where A_(tmax)/B_(tmax)are obtained.

FIGS. 6A and 6B provide examples for the correction of an active penprofile, in accordance with one or more embodiments.

Turning to FIG. 6A, an example for a correction of an active pen profile(600) is provided for a scenario in which the location of the active pendoes not overlap with the location of the finger. The left table showsan active pen profile over time. The center table shows a capacitivetouch profile over time. The right table shows a corrected active penprofile over time. Time is in the vertical direction, i.e., the topmostrows of data values are for the earliest point in time, in the tables.Each of the columns is for one electrode. The data shown in the left,center, and right tables are for the same electrodes. All three tablesprovide a heatmap representation. A diagonal fill pattern indicatesvalues above baseline (e.g., 21 to 243), a criss-cross fill patternindicates values at baseline (e.g., −17 to 20), and a vertical fillpattern indicates values below baseline (e.g., −93 to −18).

In the active pen profile (left table), the pen is stationary. Thehighest values in the active pen profile are at electrode 3, andelevated values are also found at electrode 2, suggesting that the penis stationary near electrode 3, slightly offset toward electrode 2. Overtime (moving in the downward direction in the tables), a finger isplaced in the sensing region. A pen disturbance is visible at thelocation of the finger, in the sensing region. At the location of thefinger, the values of the active pen profile are depressed (belowbaseline), due to the coupling of the inverted pen signal onto theelectrodes in proximity to the finger. However, this pen disturbancedoes not have a detrimental effect on the values for the location of theactive pen, because there is no spatial overlap.

In the capacitive touch profile, the location of the finger is visible,once the finger is in proximity to the electrodes.

In the corrected active pen profile, the pen disturbance is successfullyeliminated, while the location of the pen remains clearly visible. Thecorrection of the active pen profile to obtain the corrected active penprofile has been performed as previously described. In the example ofFIG. 6A, a fixed gain of 0.7 was used to perform the correction.

Turning to FIG. 6B, an example for a correction of an active pen profile(620) is provided for a scenario in which the location of the active penoverlaps with the location of the finger. The tables of FIG. 6B are acontinuation of the tables of FIG. 6A, at a later point in time.

In the active pen profile (left table), the pen is gradually moving fromleft to right. Initially, the highest value in the active pen profile isat electrode 9, whereas later (bottom of the table), the highest valueis at electrode 10. However, despite the gradual movement, the activepen profile does not show a smooth transition. Instead, an abrupt switchfrom electrode 9 to electrode 10 appears to occur, as indicated by thedashed line. The cause for the abrupt transition is the pen disturbance,which in the FIG. 6B causes interference at the actual location of thepen. FIGS. 2A and 2B illustrate such a situation, where the interferencecauses jagged line artifacts. The pen disturbance depresses theamplitude of the values in the active pen profile, at the pen location.

An example is illustrated in FIG. 6C, showing three adjacent values inan active pen profile (630). Because of the depressed amplitude of thevalues in the active pen profile, only one of the values is abovebaseline (dashed line). A smooth spatial interpolation between adjacentvalues is, thus, not possible. Accordingly, a gradual shift of the penlocation from one electrode to an adjacent electrode would show as anabrupt step of the active pen position between the electrodes. Thesituation is minimally better in the example adjacent values in anactive pen profile (640) of FIG. 6D, although two of the three valuesare barely above baseline. FIG. 6E illustrates a desirable scenario ofexample adjacent values in an active pen profile (650). As a result ofall three values being noticeably above the baseline, a smooth spatialinterpolation between adjacent values is possible, when the location ofthe active pen shifts.

Continuing with the discussion of FIG. 6B, in the capacitive touchprofile (center table), the location of the finger is continuouslypresent, at the location initially shown in the capacitive touch profileof FIG. 6A. Referring to the corrected active pen profile of FIG. 6B, asa result of the compensation, a smooth spatial interpolation betweenelectrodes 9 and 10 is obtained, because the compensation corrects forthe depression of the values in the active pen profile.

FIG. 7 shows a flowchart in accordance with one or more embodiments.While the various steps in the flowchart are presented and describedsequentially, one of ordinary skill will appreciate that some or all ofthe steps may be executed in different orders, may be combined oromitted, and some or all of the steps may be executed in parallel.Additional steps may further be performed. Accordingly, the scope of thedisclosure should not be considered limited to the specific arrangementof steps shown in FIG. 7 .

The flowchart of FIG. 7 depicts a method (700) for correcting touchinterference for an active pen. One or more of the steps in FIG. 7 maybe performed by the components of the input device (100). While thesubsequently described steps are described for a single capacitive touchprofile and a single active pen profile, the steps may be performed formultiple touch profiles to obtain an image frame. Further, theoperations may be repeated over time. The described operations may alsobe used in presence of multiple active pens.

In Step 702, a capacitive touch profile is obtained. The capacitivetouch profile may be obtained as previously described.

In Step 704, an active pen profile is obtained. The active pen profilemay be obtained as previously described.

In Step 706, a corrected active pen profile is obtained by adjusting theactive pen profile using the capacitive touch profile. The correctedactive pen profile may be obtained as previously described.

In Step 708, the position of the active pen in the sensing region isdetermined using the corrected active pen profile. The position of theactive pen may be obtained as previously described.

FIG. 8 shows a flowchart in accordance with one or more embodiments.While the various steps in the flowchart are presented and describedsequentially, one of ordinary skill will appreciate that some or all ofthe steps may be executed in different orders, may be combined oromitted, and some or all of the steps may be executed in parallel.Additional steps may further be performed. Accordingly, the scope of thedisclosure should not be considered limited to the specific arrangementof steps shown in FIG. 8 .

The flowchart of FIG. 8 depicts a method (800) for correcting touchinterference for an active pen using multiple axes. The gain may befiltered and adjusted when optimal tuning regions (e.g., receiverelectrode 505 in FIG. 5 ) are identified and confirmed. By way ofexample, tuning may not be performed if the pen is located on an edgeelectrode. Additionally, the tuning may be applied to electrodes on thevertical axis and to electrodes on the horizontal axis and may be usedseparately for each axis. If one axis is blocked from tuning for severalseconds, then the other axis may provide assistance and update the gainfor both axes.

One or more of the steps in FIG. 8 may be performed by the components ofthe input device. While the subsequently described steps are describedfor a single capacitive touch profile and a single active pen profile,the steps may be performed for multiple touch profiles to obtain animage frame. Further, the operations may be repeated over time. Thedescribed operations may also be used in presence of multiple activepens.

In Step 802, the input device obtains a first capacitive touch profilefrom multiple receiver electrodes along a first axis of the sensingregion.

In Step 804, the input device makes a determination that each capacitivemeasurement, in the first capacitive touch profile, affected by an inputobject is also affected by an active pen. Because each capacitivemeasurement affected by the input object is also affected by the activepen, the capacitive measurements at the input object location may not beused to adjust the active pen profile on the first axis.

In Step 806, the input device obtains a second capacitive touch profilefrom multiple receiver electrodes along a second axis of the sensingregion. The second capacitive touch profile may be obtained responsiveto the determination of Step 804 or independently of the determinationof Step 804.

In Step 808, the input device selects, responsive to the determination,the second capacitive touch profile to adjust the active pen profile. Inone or more embodiments, the input device determines that at least onecapacitive measurement at the input object location in the secondcapacitive touch profile is not affected by the active pen.

In Step 810, the input device obtains an active pen profile. The activepen profile may be obtained as previously described.

In Step 812, the input device obtains a corrected active pen profile byadjusting the active pen profile using the second capacitive touchprofile.

In Step 814, the input device determines the position of the active penin the sensing region using the corrected active pen profile.

In some embodiments, for the E0, E1, E2 regions on the right side ofFIG. 5 , projected transcapacitance profiles may be used instead ofabsolute sensing profiles. Similarly, for the B_(tmax) electrode on theright side of FIG. 5 , projected transcapacitance profiles may be usedinstead of absolute sensing profiles.

It is noted that scaling may be used so that one axis (vertical orhorizontal) can provide a tuning value for the other axis, when theother axis is blocked and cannot update an active pen profile for aperiod of time. The scaling may be a ratio, for example 70%, that isknown or measured in advance and may be based on phone model. Forexample, suppose the X axis has a tuning value of 700, the Y axis hasbeen blocked and needs a tuning value. The X tuning value may bemultiplied by 70% to get 490, which is then used by the Y axis.

Embodiments of the disclosure, thus, provide methods and systems forcorrecting touch interference for an active pen. While not shown,additional elements may be included. For example, in one embodiment, astate machine is configured to determine whether the method forcorrecting touch interference is to be performed or not. The statemachine may check whether an active pen and a touch area simultaneouslypresent in the sensing region. The state machine may execute the method,only if the simultaneous presence is detected. The state machine mayotherwise skip the execution of the method, to avoid a possibleintroduction of artifacts by an unnecessary correction operation. Animplementation of the method and system as described may further includevarious filtering operations. For example, a temporal filter may beapplied to the active pen position to address issues that may resultfrom the finger or palm in the sensing area moving at a high velocity.The filter, in this scenario may address a mismatch between touchsensing rates (e.g., 60 Hz) and active pen sensing rates (e.g., 240 Hz)to avoid motion artifacts in the pen trajectory.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.

1. A method of capacitive sensing, comprising: obtaining a capacitivetouch profile from a plurality of receiver electrodes disposed in asensing region of an input device; obtaining an active pen profile,different from the capacitive touch profile, from the plurality ofreceiver electrodes; adjusting, using the capacitive touch profile, theactive pen profile to obtain a corrected active pen profile; anddetermining a position of an active pen in the sensing region, using thecorrected active pen profile.
 2. The method of claim 1, whereinobtaining the active pen profile comprises: receiving emissions of theactive pen, by the plurality of receiver electrodes.
 3. The method ofclaim 1, wherein obtaining the active pen profile comprises a quadraturedemodulation.
 4. The method of claim 1, wherein the corrected active penprofile is obtained by: adding the capacitive touch profile to theactive pen profile, after scaling the capacitive touch profile by again.
 5. The method of claim 4, wherein the corrected active pen profileis further obtained by: determining the gain based on a ground mass. 6.The method of claim 5, wherein a previously obtained gain is used as thegain.
 7. The method of claim 1, further comprising: prior to thecorrected active pen profile being obtained: determining whether a touchis present in the sensing region, in addition to the active pen, andbased on determining that the touch is present, obtaining the correctedactive pen profile.
 8. The method of claim 1, wherein the capacitivetouch profile is a first capacitive touch profile and is along a firstaxis of the sensing region and wherein the method further comprises:obtaining a second capacitive touch profile along a second axis of thesensing region; making a determination that each capacitive measurement,in the first capacitive touch profile, affected by an input object isalso affected by an active pen; and selecting, responsive to thedetermination, the second capacitive touch profile to adjust the activepen profile.
 9. The method of claim 8, wherein the active pen profile isa first active pen profile and is along the first axis of the sensingregion and wherein the method further comprises: determining a gain fromthe second capacitive touch profile, wherein adjusting the first activepen profile uses the gain; scaling the gain for the second axis toobtain a scaled gain; obtaining a second active pen profile along thesecond axis of the sensing region; and adjusting the second active penprofile using the scaled gain.
 10. An input device, comprising: aplurality of receiver electrodes disposed in a sensing region; and aprocessing system configured to: obtain a capacitive touch profile fromthe plurality of receiver electrodes, obtain an active pen profile,different from the capacitive touch profile, from the plurality ofreceiver electrodes, adjust, using the capacitive touch profile, theactive pen profile to obtain a corrected active pen profile, anddetermine a position of an active pen in the sensing region, using thecorrected active pen profile.
 11. The input device of claim 10, whereinobtaining the active pen profile comprises a quadrature demodulation.12. The input device of claim 10, wherein the corrected active penprofile is obtained by: adding the capacitive touch profile to theactive pen profile, after scaling the capacitive touch profile by again.
 13. The input device of claim 11, wherein the corrected active penprofile is further obtained by: determining a gain based on a groundmass.
 14. The input device of claim 10, wherein the processing system isfurther configured to: prior to the corrected active pen profile beingobtained: determine whether a touch is present in the sensing region, inaddition to the active pen, and based on determining that the touch ispresent, obtain the corrected active pen profile.
 15. A processingsystem, configured to: obtain a capacitive touch profile from aplurality of receiver electrodes disposed in a sensing region of aninput device; obtain an active pen profile, different from thecapacitive touch profile, from the plurality of receiver electrodes;adjust, using the capacitive touch profile, the active pen profile toobtain a corrected active pen profile; and determine a position of anactive pen in the sensing region, using the corrected active penprofile.
 16. The processing system of claim 15, wherein obtaining theactive pen profile comprises: receiving emissions of the active pen, bythe plurality of receiver electrodes.
 17. The processing system of claim15, wherein obtaining the active pen profile comprises a quadraturedemodulation.
 18. The processing system of claim 15, wherein thecorrected active pen profile is obtained by: adding the capacitive touchprofile to the active pen profile, after scaling the capacitive touchprofile by a gain.
 19. The processing system of claim 18, wherein thecorrected active pen profile is further obtained by: determining thegain based on a ground mass.
 20. The processing system of claim 15,wherein the processing system is further configured to: prior to thecorrected active pen profile being obtained: determine whether a touchis present in the sensing region, in addition to the active pen, andbased on determining that the touch is present, obtaining the correctedactive pen profile.